I would like to use Resilience4j to deal with fault tolerance, I am using CircuitBreaker and TimerLimit.
I would like to separate business logic of fault tolerance behavior, to not "dirty" my business code.
So, I am thinking to use Command pattern to execute my methods that will be treat, like Hystrix do with HystrixCommand.
Example:
public class MyCommand {
private static final CircuitBreaker circuitBreaker;
private Long param1, param2;
private MyService myService;
private static final TimeLimiter timeLimiter;
static {
long ttl = 50000;
TimeLimiterConfig configTimerLimit
= TimeLimiterConfig.custom().timeoutDuration(Duration.ofMillis(ttl)).build();
timeLimiter = TimeLimiter.of(configTimerLimit);
// I got the configuration from a class that I created.
circuitBreaker = CircuitBreaker.of("my", CircuitBreakerConfigOptions.defaultForExternalService());
}
public MyCommand(Long param1, Long param2, MyService myService) {
this.param1 = param1;
this.param2 = param2;
this.myService = myService;
}
public String run() {
Callable<String> stringCallable = TimeLimiter.decorateFutureSupplier(timeLimiter,
() -> CompletableFuture.supplyAsync(() -> myService.hello(param1, param2)));
Callable<String> callable = CircuitBreaker.decorateCallable(circuitBreaker, stringCallable);
return Try.of(callable::call).recover(t -> fallback(t)).get();
}
protected String fallback(Throwable throwable) {
Callable<String> stringCallable = TimeLimiter.decorateFutureSupplier(timeLimiter,
() -> CompletableFuture.supplyAsync(() -> myService.otherHello(param1, param2)));
return Try.of(stringCallable::call).getOrElse("Fallback");
}
}
Calling in my Controller:
@ApiOperation(value = "Only to test")
@GetMapping(value = "/execute", produces = MediaType.APPLICATION_JSON)
public String execute() {
return new MyCommand(1L, 2L, new MyService()).run();
}
My doubts:
1 - In this case, circuitBreaker really needs to be static, because I understood that the same object needs to be shared between the same method that you want to threat, I am right?
2 - How I have many instances of this application, circuitBreaker works individually for each instance? I am right?
Since it seems that you are using Spring Boot, you could use the resilience4j-spring-boot-2 starter module which also has support for annotations.